The Voyager program comprises without a doubt the most prolific planetary exploration mission ever launched. Even at this point in time the two Voyager probes continue their valiant work as they explore the outer reaches of the solar system.
The genesis of the Voyager program
In the 1970s, astronomers at NASA wanted to take advantage of the position of the giant planets in the solar system to explore those distant bodies. That particular position made it possible to use the gravity of one planet to propel and accelerate a probe to the next planet. Hence were the two Voyager probes launched in 1977.
Volcanoes on one of Jupiter’s moons
Voyager 1 was the first to overfly the planet Jupiter, in March 1979. It would be followed a few months later by its sister spacecraft, Voyager 2. The probes then began sending back images that were high-resolution for the time. It was the start of a series of discoveries that continues to fascinate astronomers even today.
One of the most impressive of these is the presence of active volcanoes on the moon Io, which is just a little larger than our own Moon. The surface of Europa, another of Jupiter’s moons, pointed to the likelihood that its crust of ice hides an ocean beneath it – something that would be confirmed a number of years later by the probe Galileo.
As it journeyed away from Jupiter, Voyager 1 also discovered thin rings around the planet.
The complexity of Saturn’s rings
The overflight of Saturn the following year also had its share of discoveries in store. The probes revealed a highly complex system of rings, subdivided into thousands of smaller rings. Even dust could be seen floating above them.
The atmosphere of the gas giant proved to be more turbulent than expected, presenting us with images of great beauty.
As a bonus, close-up images of the moon Mimas become a wonderful tip of the hat to the Death Star in the movie Star Wars.
Afterwards, Voyager 1’s trajectory was modified to propel it above the planets’ orbital plane. Now racing at a speed of over 61,000 km/h, the probe was the fastest spacecraft we’d ever launched into space.
Voyager 2 visits Uranus and Neptune
Voyager 2 took over planetary exploration by flying over Uranus in 1986. This time it was the planet’s moons that stole the show by revealing surfaces marked by numerous impacts. The clear winner was Miranda, which has immense fissures at angles of close to 90 degrees. Some astronomers believe that the moon may have been shattered into a number of pieces at the beginnings of the solar system, and later re-formed.
In 1989, Voyager 2 wrapped up the grand tour of the planets by flying over Neptune. We discovered a planet with a turbulent atmosphere in which the most violent winds in the solar system were recorded. Even hydrogen geysers were observed on the moon Triton.
Exploring the outer limits of the solar system – and beyond
The Voyager probes are carrying on with their mission by exploring the interplanetary medium. They’ve even reached the heliopause, the place where interstellar matter dominates. They thus became the first spacecraft to leave the solar system.
In order to extend the mission, a number of instruments were shut down to conserve the life of the nuclear batteries on board the probes. Before turning off its cameras, Voyager 1 took a striking family photo of the planets in our solar system. The batteries should allow the Voyager probes to operate until 2025.
To find out more about this mission, I invite you to visit the Planétarium and see the immersive film Voyager: The Never-Ending Journey.